The invention relates generally to a method and apparatus for establishing, examining, or analyzing the structure of a solid, and in particular, to a method and apparatus for detecting flaws in a solid.
Many methods and apparatus exist today for making measurements upon a solid. The solid may be for example a cast iron manufactured part, the human body, or the earth (during, for example, seismic investigations). The prior art methods and apparatus include X-ray examination, ultrasonic examination, visual examination, explosive and destructive techniques. The present invention is directed to improvements in the ultrasonic examination of solids.
The utlrasonic examination of solids is generally considered a well established art. Conventional prior art systems use either a pulse echo technique, which is most common, or a continuous interrogation signal using, for example, a random noise generator. In the pulse echo technique, a short pulse is directed toward the solids being examined and the returning echos are received and recorded. The returning signal data is processed to determine the existence of unwanted flaws or other structural irregularities. This technique unfortunately has a limited average power input to the solid, and, as the shape of the solid to be examined becomes more complex, provides increasingly poor performance. Also a wide band receiver is required which often results in a poor signal to noise ratio.
The continuous signal techniques, provided for example by Proctor, U.S. Pat. No. 3,228,232, provide limited data, and have serious shortcomings as the geometry of the object being examined becomes more complex.
It is therefore an object of the invention to provide an apparatus and method for examining a solid which are capable of interrogating a solid of simple or complex shape. Other objects of the invention are a method and apparatus which are reliable, which provide significantly greater information than is available from earlier techniques, and which can be adapted to either real time investigations or to investigations in which later processing is available.
Other objects of the invention include an apparatus and method which is flexible, which provide extremely high detection rates, which has low false alarm rates, and to which statistical estimation techniques can be adapted for increasing both reliability and performance of the apparatus.